Rockwell Automation T8444 Trusted TMR Pulse Generator and Monitoring Module - Manual (Page 12)

Trusted
TM
Module T8444
Issue 09 Apr 10 PD-T8444 12
1.5. Line Monitoring
The module automatically monitors the channel line fault status. These are reported back to the
application and are represented below.
Description Line Fault Status
Field Short Circuit 1
Output Energised (On) 0
No Load, Field Open Circuit 1
Output De-energised (Off) 0
No Field Supply Voltage 1
Table 1 Line Monitoring Fault Status
1.6. Housekeeping
The module automatically performs local measurements of several on-board signals that can be used
for detailed troubleshooting and verification of module operating characteristics. Measurements are
made within each slice’s HIU and FIU to determine the condition of the power supplies and common
services such as the temperature of the HIU.
1.7. Fault Detection/Testing
From the IMB to the field connector, the I/O module contains extensive fault detection and integrity
testing. Most testing is performed in a non-interfering mode. Data input from the IMB is stored in
redundant error-correcting RAM on each slice portion of the HIU. Received data is voted on by each
slice. All data transmissions include a confirmation response from the receiver.
Periodically, the TMR Processor commands the onboard DSPs to perform a Safety Layer Test. The
SLT results in the DSP verifying with the TMR Processor its ability to process data with integrity. In
addition, the DSP uses Cyclical Redundancy Checks (CRC) to verify the variables and configuration
stored in Flash memory.
Between the HIU and FIU are a series of optically isolated links for data and power. The data link is
synchronised and monitored for variance. Both FIU and HIU have onboard temperature sensors to
characterise temperature-related problems. Each FIU is also fitted with a condensation sensor.
The power supplies for both the HIU and FIU boards are redundant, fully instrumented and testable.
Together these assemblies form a Power Integrity Sub System.